The match comes four years after Harlequins' lowest point - Bloodgate. It was in the 2009 quarter-final against Leinster that O'Shea's predecessor Dean Richards instructed wing Tom Williams to bite on a fake blood capsule so he could engineer a late substitution. Harlequins lost 6-5 and their plot was rumbled which resulted in Richards receiving a three-year ban.

Quins eventually opted for O'Shea as Richards' long-term successor meaning the Irishman left his post with the English Institute of Sport (EIS). Since then Harlequins have come on leaps and bounds with the high point being their Aviva Premiership triumph last season.

But O'Shea believes that the weekend's clash will see Harlequins elevated to a new level of intensity. "This Sunday will be the best day The Stoop has witnessed in terms of atmosphere and occasion," O'Shea said. "I was watching the Champions League last night and thinking 'that's the level we are at in rugby'.

"One of the first books I was given by (then chief executive) Mark Evans when I came into the club was a history of Harlequins. Every person, every team has a history. There are good and bad chapters in every history. You want to go and create different chapters.

"We just can't wait to get into the quarter-final this weekend and help this club get to a first Heineken Cup semi-final in its history. There is no tomorrow in games like this. Munster's journey of heartache and loss to ultimately winning it is one of the great stories of the Heineken Cup. They will come absolutely full on and we will be there to meet them and greet them in the right way."

O'Shea conceded that it was a tough decision he made to leave the EIS but it was the group of young players at Quins who inspired him to take on the role. He added: "The debate I had with my wife over leaving the EIS was 'why am I leaving a safe job in the public service for a job where I could be sacked within six games?'

"The club was not tainted in that the people and structures and players were in rude health. From bad can come good. It is a great club to be part of. I love rugby and the game and the guys here had incredible amount of ability. You back them that you are going to get a good chance to achieve something."

The desire O'Shea has to see his project through at Harlequins is strong enough to resist even the lure of his country, with Ireland now hunting a new head coach. O'Shea has confirmed his commitment to Harlequins and he would like to extend his contract beyond 2014. It is not just the present he believes is bright.

"Over the last three seasons we have won three trophies. We are in the quarter-finals of the Heineken Cup and we are in the Premiership play-off places," O'Shea said. "These next eight weeks are the eight weeks you want. It could be nothing - it could be all. Hopefully it is going to be great end.

"We are very excited about the group of players we have and how far we still have left to improve as a team. There are so many good young players at this club. We won the A League. You look at the team that won the Anglo-Welsh Cup. You want to be around and see that grow. It is bloody exciting."